Comparison of the indentation and elasticity of E. coli and its spheroplasts by AFM

Atomic force microscopy (AFM) provides a unique opportunity to study live individual bacteria at the nanometer scale. In addition to providing accurate morphological information, AFM can be exploited to investigate membrane protein localization and molecular interactions on the surface of living cells. A prerequisite for these studies is the development of robust procedures for sample preparation. While such procedures are established for intact bacteria, they are only beginning to emerge for bacterial spheroplasts. Spheroplasts are useful research models for studying mechanosensitive ion channels, membrane transport, lipopolysaccharide translocation, solute uptake, and the effects of antimicrobial agents on membranes. Furthermore, given the similarities between spheroplasts and cell wall-deficient (CWD) forms of pathogenic bacteria, spheroplast research could be relevant in biomedical research. In this paper, a new technique for immobilizing spheroplasts on mica pretreated with aminopropyltriethoxysilane (APTES) and glutaraldehyde is described. Using this mounting technique, the indentation and cell elasticity of glutaraldehyde-fixed and untreated spheroplasts of E. coli in liquid were measured. These values are compared to those of intact E. coli. Untreated spheroplasts were found to be much softer than the intact cells and the silicon nitride cantilevers used in this study.

Antiulcerogenic potential of Strychnos potatorum Linn seeds on aspirin plus pyloric ligation-induced ulcers in experimental rats

Strychnos potatorum (Fam: Loganiaceae) Linn seeds are useful in the treatment of gastropathy in Indian traditional system of medicine. The present study describes the antiulcerogenic potential of S. potatorum Linn seeds on aspirin plus pyloric ligation (Aspirin+PL)-induced gastric ulcer model to substantiate its folklore claim. The seed powder (SPP) and aqueous extract of the seeds (SPE) at two doses 100 and 200 mg/kg, p.o. prevented ulcer formation by decreasing acid secretory activity and increasing the mucin activity in rats. The antiulcerogenic potential was further confirmed by the histopathological studies of stomach mucosa. The results indicate that SPP and SPE exhibit antiulcerogenic activity by both antisecretory and mucoprotective actions. The mucoprotective action of SPP and SPE may be due to the presence of polysaccharides in seeds. The antiulcerogenic potential of SPP and SPE was compared with the standard antiulcer drug, ranitidine.

Tropical malabsorption

Malabsorption is an important clinical problem both in visitors to the tropics and in native residents of tropical countries. Infections of the small intestine are the most important cause of tropical malabsorption. Protozoal infections cause malabsorption in immunocompetent hosts, but do so more commonly in the setting of immune deficiency. Helminth infections occasionally cause malabsorption or protein-losing enteropathy. Intestinal tuberculosis, chronic pancreatitis and small-bowel bacterial overgrowth are important causes of tropical malabsorption. In recent years, inflammatory bowel disease and coeliac disease have become major causes of malabsorption in the tropics. Sporadic tropical sprue is still an important cause of malabsorption in adults and in children in South Asia. Investigations to exclude specific infective, immunological or inflammatory causes are important before considering tropical sprue as a diagnosis. This article briefly reviews the management of tropical sprue and presents an algorithm for its investigation and management.

Automated image analysis of atomic force microscopy images of rotavirus particles

A variety of biological samples can be imaged by the atomic force microscope (AFM) under environments that range from vacuum to ambient to liquid. Generally imaging is pursued to evaluate structural features of the sample or perhaps identify some structural changes in the sample that are induced by the investigator. In many cases, AFM images of sample features and induced structural changes are interpreted in general qualitative terms such as markedly smaller or larger, rougher, highly irregular, or smooth. Various manual tools can be used to analyze images and extract more quantitative data, but this is usually a cumbersome process. To facilitate quantitative AFM imaging, automated image analysis routines are being developed. Viral particles imaged in water were used as a test case to develop an algorithm that automatically extracts average dimensional information from a large set of individual particles. The extracted information allows statistical analyses of the dimensional characteristics of the particles and facilitates interpretation related to the binding of the particles to the surface. This algorithm is being extended for analysis of other biological samples and physical objects that are imaged by AFM.

Measuring cell surface elasticity on enteroaggregative Escherichia coli wild type and dispersin mutant by AFM

Enteroaggregative Escherichia coli (EAEC) is pathogenic and produces severe diarrhea in humans. A mutant of EAEC that does not produce dispersin, a cell surface protein, is not pathogenic. It has been proposed that dispersin imparts a positive charge to the bacterial cell surface allowing the bacteria to colonize on the negatively charged intestinal mucosa. However, physical properties of the bacterial cell surface, such as rigidity, may be influenced by the presence of dispersin and may contribute to pathogenicity. Using the system developed in our laboratory for mounting and imaging bacterial cells by atomic force microscopy (AFM), in liquid, on gelatin coated mica surfaces, studies were initiated to measure cell surface elasticity. This was carried out in both wild type EAEC, that produces dispersin, and the mutant that does not produce dispersin. This was accomplished using AFM force-distance (FD) spectroscopy on the wild type and mutant grown in liquid or on solid medium. Images in liquid and in air of both the wild-type and mutant grown in liquid and on solid media are presented. This work represents an initial step in efforts to understand the pathogenic role of the dispersin protein in the wild-type bacteria.

Studies on hepatoprotective and antioxidant actions of Strychnos potatorum Linn. seeds on CCl4-induced acute hepatic injury in experimental rats

Strychnos potatorum Linn. seeds are used in the Indian traditional system of medicine for the treatment of hepatopathy, nephropathy, gonorrhoea, leucorrhoea, gastropathy, bronchitis, chronic diarrhoea, strangury, renal and vesicle calculi, diabetes and eye diseases. The present study describes the hepatoprotective and antioxidant activities of the seed powder (SPP) and aqueous extract (SPE) of Strychnos potatorum seeds against CCl4-induced acute hepatic injury. Hepatic injury was achieved by injecting 3 ml/kg, s.c. of CCl4 in equal proportion with olive oil. Both SPP and SPE at the doses 100 and 200 mg/kg, p.o. offered significant (p < 0.001) hepatoprotective action by reducing the serum marker enzymes like serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT). They also reduced the elevated levels of ALP and serum bilirubin. Reduced enzymic and nonenzymic antioxidant levels and elevated lipid peroxide levels were restored to normal by administration of SPP and SPE. Histopathological studies further confirmed the hepatoprotective activity of SPP and SPE when compared with the CCl4 treated control groups. The results obtained were compared with Silymarin (50 mg/kg, p.o.), the standard drug. In conclusion, SPE (200 mg/kg, p.o.) showed significant hepatoprotective activity similar to that of the standard drug, Silymarin (50 mg/kg, p.o.).

Hepatoprotective and antioxidant effects of Hygrophila auriculata (K. Schum) Heine Acanthaceae root extract

Hygrophila auriculata (K. Schum) Heine (syn. Asteracantha longifolia Nees, Acanthaceae) was widely used in the Indian systems of medicine for the treatment of various liver ailments. The hepatoprotective activity of the aqueous extract of the roots was studied on CCl(4)-induced liver toxicity in rats. The activity was assessed by monitoring the various liver function tests, viz. alanine transaminase, aspartate transaminase (AST), alkaline phosphatase (ALP), total protein and total bilirubin. Furthermore, hepatic tissues were subjected to histopathological studies. The root extract was also studied for its in vitro antioxidant activity using ferric thiocyanate (FTC) and thiobarbituric acid (TBA) methods. The extract exhibited significant hepatoprotective and antioxidant activities.

Anti-inflammatory activity of Justicia prostrata gamble in acute and sub-acute models of inflammation

In this study, the aqueous (AQJP) and alcoholic (ALJP) extracts of the whole plant of Justicia prostrata Gamble (Acanthaceae) were screened for their acute and subacute anti-inflammatory activities using carrageenan-induced acute inflammation and cotton-pellet-induced granuloma (subacute inflammation), respectively, in rats. In the carrageenan-induced rat paw oedema model, both extracts were found to exhibit maximum reduction in paw volume at the first hour in a dose-dependent manner. At the dose of 500 mg/kg p.o., both extracts AQJP and ALJP showed maximum inhibition (51.39% and 62.5%, respectively) in rat paw oedema volume at the first hour of carrageenan-induced acute inflammation. In the cotton pellet granuloma assay, AQJP and ALJP at the dose of 500 mg/kg p.o. suppressed the transudative, exudative and proliferative phases of chronic inflammation. These extracts were able to (i) reduce the lipid peroxide content of exudates and liver and (ii) normalize the increased activity of acid and alkaline phosphatases in serum and liver of cotton pellet granulomatous rats. Preliminary phytochemical screening revealed the presence of lignans, triterpenes and phenolic compounds in ALJP, whereas phenolic compounds and glycosides in AQJP. The anti-inflammatory properties of these extracts may possibly be due to the presence of phenolic compounds. The anti-inflammatory effects produced by the extracts at the dose of 500 mg/kg, p.o. was comparable with the reference drug diclofenac sodium (5 mg/kg p.o.).

Hyperglycaemia as an indicator of concurrent acute pancreatitis in fulminant hepatic failure associated with hepatitis B infection

Pancreatitis occurring concurrently with fulminant hepatic failure (FHF) is primarily detected on autopsy and is seldom clinically apparent. We report a fatal case of FHF in a 25-year-old woman which was related to acute hepatitis B infection. In this patient, hyperglycaemia needing insulin infusions led to the detection of acute pancreatitis. FHF complicated by acute pancreatitis has a poor prognosis. A high index of suspicion is necessary for its diagnosis. The role of orthotopic liver transplantation and use of antiviral therapies need further evaluation in this situation.

Antiulcerogenic effect of Justicia prostrata Gamble

Antiulcerogenic effect of the alcoholic (ALJP) and aqueous (AQJP) extracts of the whole plant of Justicia prostrata was studied in aspirin+pylorus ligated rat models and analysed for gastric volume, ulcer index, free and total acidity. Biochemical parameters like total proteins, total hexoses, hexosamine, fucose and sialic acid were also estimated. Both extracts (ALJP and AQJP) significantly reduced both the gastric volume and the acidity of gastric juice. It also significantly promoted gastric mucus secretion by increasing total carbohydrates and decreasing the protein concentration in aspirin+ pylorus ligated rats. The results suggest that both the extracts (ALJP and AQJP) possess antiulcer activity, whereas AQJP is more effective when compared with ALJP in aspirin+pylorus ligated rat models. The results were compared with the standard drug Rantidine, a H2 receptor antagonist.

Assessing the severity of hepatic encephalopathy

The diagnosis of hepatic encephalopathy (HE) is based mostly on clinical criteria. It is important to assess the severity of HE quantitatively for both clinical practice and research; however, this remains a difficult and challenging problem. Modalities like psychometric tests, electroencephalography, evoked potentials, and several innovative biochemical indices have shown promise in this regard. No single parameter or index has yet been shown to be infallible in assessing the severity of HE.

Efficient Solution Algorithms for Factored MDPs

This paper addresses the problem of planning under uncertainty in large Markov Decision Processes (MDPs). Factored MDPs represent a complex state space using state variables and the transition model using a dynamic Bayesian network. This representation often allows an exponential reduction in the representation size of structured MDPs, but the complexity of exact solution algorithms for such MDPs can grow exponentially in the representation size. In this paper, we present two approximate solution algorithms that exploit structure in factored MDPs. Both use an approximate value function represented as a linear combination of basis functions, where each basis function involves only a small subset of the domain variables. A key contribution of this paper is that it shows how the basic operations of both algorithms can be performed efficiently in closed form, by exploiting both additive and context-specific structure in a factored MDP. A central element of our algorithms is a novel linear program decomposition technique, analogous to variable elimination in Bayesian networks, which reduces an exponentially large LP to a provably equivalent, polynomial-sized one. One algorithm uses approximate linear programming, and the second approximate dynamic programming. Our dynamic programming algorithm is novel in that it uses an approximation based on max-norm, a technique that more directly minimizes the terms that appear in error bounds for approximate MDP algorithms. We provide experimental results on problems with over 10^40 states, demonstrating a promising indication of the scalability of our approach, and compare our algorithm to an existing state-of-the-art approach, showing, in some problems, exponential gains in computation time.

Faecal lactoferrin as a predictor of positive faecal culture in south Indian children with acute diarrhoea

Faecal lactoferrin, an iron-based glycoprotein found concentrated in secondary granules of neutrophils, may serve as a surrogate marker of inflammation in the intestine. We evaluated the usefulness of faecal lactoferrin as a predictor of infection with invasive enteropathogens in 262 children with diarrhoea. Lactoferrin at a dilution of 1:50 had the highest sensitivity for detection not only of conventionally cultured invasive enteropathogens but also of all other enteropathogens. Neither individual clinical symptoms nor the identification of faecal leucocytes by microscopy significantly predicted isolation of invasive enteropathogens from the faeces of children with diarrhoea. Faecal lactoferrin is a simple test which showed promise in predicting which children with diarrhoea are likely to be infected with invasive pathogens and can be incorporated as a screening test before faecal cultures are undertaken in this population.

Evaluation of anti-diarrhoeal activity in seed extracts of Mangifera indica

Mangifera indica is commonly grown in many parts of the world. Its seeds have been used for anti-diarrhoeal activity in Indian traditional medicine. This study evaluates the potential anti-diarrhoeal activity of methanolic (MMI) and aqueous (AMI) extracts of seeds of M. indica in experimental diarrhoea, induced by castor oil and magnesium sulphate in mice. Both MMI and AMI were given orally in the dose of 250 mg/kg, showed significant anti-diarrhoeal activity comparable with that of the standard drug loperamide. However, only MMI significantly reduced intestinal transit in charcoal meal test as compared with atropine sulphate (5 mg/kg; im). The in vitro antimicrobial activity of MMI and AMI showed variable results. While, AMI significantly inhibited growth of Streptococcus aureus and Proteus vulgaris, both MMI and AMI did not show any significant effect on growth of E. coli and Klebsiella. The results illustrate that the extracts of M. indica have significant anti-diarrhoeal activity and part of the activity of MMI may be attributed to its effect on intestinal transit.

Stakeholder Value Equilibration and the Entrepreneurial Process

This lecture explores the possibility of a useful dialogue between the fields of entrepreneurship and business ethics for mutual benefit. Although these two fields have much to offer each other, they have developed largely independently of each other. The lecture argues that entrepreneurship has a role to play in stakeholder theory and, relatedly, that stakeholder theory enriches our understanding of the entrepreneurial process. The lecture introduces the idea that a firm is an equilibrating mechanism, and then asks two questions, namely, “What are the properties of a fair and efficient equilibrating mechanism?” and “What alternative mechanisms would render the firm an effective reconciler of competing claims?” The lecture interprets the stakeholder literature to offer three alternative mechanisms to ensure a fair and efficient equilibrating system. The first mechanism is embodied in a person (the moral manager), the second is embodied in a process (the bargaining process), and the third is embodied in an external (to the firm) institution (the visible hand of law and government). To these three, the lecture adds a fourth mechanism from an entrepreneurship perspective, and explores the implications of this perspective to the stakeholder literature.